Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With etchant gas supply or exhaust structure located outside...
Reexamination Certificate
2001-10-16
2002-10-22
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With etchant gas supply or exhaust structure located outside...
C156S345340, C156S345480, C118S715000, C118S7230ER, C118S7230IR
Reexamination Certificate
active
06468385
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for operating and etch chamber with reduced contamination and more particularly, relates to an apparatus and a method for preventing residual etchant gas in the middle chamber of an etch chamber from attacking metal sidewalls of the middle chamber by providing a bypass exhaust conduit to evacuate any residual etchant gas.
BACKGROUND OF THE INVENTION
In the fabrication of semiconductor devices, particularly in the fabrication of submicron scale semiconductor devices, profiles obtained in etching process are very important. A careful control of a surface etch process is therefore necessary to ensure directional etching. In conducting an etching process, when an etch rate is considerably higher in one direction than in the other directions, the process is called anisotropic. A reactive ion etching (RIE) process assisted by plasma is frequently used in an anisotropic etching of various material layers on top of semiconductor substrate. In plasma enhanced etching processes, the etch rate of a semiconductor material is frequently larger than the sum of the individual etch rates for ion sputtering and individual etching due to a synergy in which chemical etching is enhanced by ion bombardment.
To avoid subjecting a semiconductor waiver to high-energy ion bombardment, the wafer may also be placed downstream from the plasma and outside the discharge area. Downstream plasma reactors etches more in an isotropic manner since there are no ions to induce directional etching. The downstream reactors are frequently used for removing resist or other layers of material where patterning is not critical. In a downstream reactor, radio frequency may be used to generate long-lived active species for transporting to a wafer surface relocated remote from the plasma. Temperature control problems and radiation damage are therefore significantly reduced in a downstream reactor. Furthermore, the wafer holder can be heated to a precise temperature to increase the chemical reaction rate, independent of the plasma.
In a downstream reactor, an electrostatic wafer holding device known as an electrostatic chuck is frequently used. The electrostatic chuck attracts and holds a wafer positioned on top electrostatically. The electrostatic chuck method for holding a wafer is highly desirable in the vacuum handling and processing of wafers. An electrostatic chuck device can hold and move wafers with a force equivalent to several tens of Torr pressure, in contrast to a conventional method of holding wafers by a mechanical clamping method.
Referring initially to
FIG. 1
, wherein a conventional inductively coupled plasma etched chamber
10
is shown. In the etch chamber
10
, which typically represents one that is commercially available as a LAM TCP etcher, the plasma source is a transformer-coupled source that generates a high density, low pressure plasma away from a wafer surface. The plasma source allows an independent control of ion flux and ion energy. The plasma can be generated by a flat spiral coil (not shown), i.e. an inductive coil separated from the plasma by a dielectric plate
12
which is normally fabricated of a ceramic material with a gas inlet
14
provided therein. The ceramic plate
12
may be a dielectric window made of a substantially transparent material such as quartz to facilitate visual observation of the middle chamber
20
. The middle chamber
20
is further formed by a bottom ceramic plate
16
equipped with an apertured opening
18
for allowing a plasma to pass thereto. The sidewall
22
of the middle chamber
20
is normally formed of a metallic material, such as aluminum, with an anodized aluminum surface. The top ceramic plate
12
, the bottom ceramic plate
16
and the metallic sidewall
22
form a self-contained chamber, i.e. the middle chamber
20
which has a first cavity
24
therein.
A wafer
30
is positioned on the electrostatic chuck (or ESC)
26
sufficiently away from the RF coil (not shown) such that it is not affected by the electromagnetic field generated by the RF coil. A typical LAM TCP plasma etcher enables a high density plasma to be produced and a high etch rate to be achieved. In the plasma etcher
10
, an inductive supply and a bias supply are further used to generate the necessary plasma field. In a typical inductively coupled RF plasma etcher
10
, shown in
FIG. 1
, a source frequency of 13.5 MHZ and a substrate bias frequency of 13.5 MHZ are utilized such that ion density of about 0.5~2.0×10
12
cm
3
is obtained at the wafer level, while electron temperature of 3.5~6.0 eV and a chamber pressure of 1~25 mTorr are achieved.
In the plasma chamber
10
, after the wafer
30
is etched in the main chamber
32
, the chamber is normally evacuated of the etchant gas from the middle chamber
20
and from the main chamber
32
by a turbo pump
34
controlled by a gate valve
36
. The turbo pump is further connected to a dry pump
38
through a control valve
42
. When the pressure in the chamber is too high, in order not to damage the turbo pump
34
, control valve
42
closes while control valve
44
opens to allow the chamber to be evacuated by the dry pump
38
directly. Simultaneous with the pumping process, an inert purge gas such as nitrogen is flown into the middle chamber
20
and the main chamber
32
through gas inlet
14
to further facilitate the removal of residual etchant gas.
In the conventional plasma chamber
10
, a problem caused by the residual etchant gas left in the cavity
24
of the middle chamber
20
frequently occurs. The residual etchant gas cannot be evacuated from cavity
24
due to the small holes in the apertured opening
18
situated in the bottom ceramic plate
16
. The small holes do not allow a fast flow rate so that the evacuation of the middle chamber
20
is ineffective. The residual etchant gas left in cavity
24
attacks the metal sidewall
22
and thus causing corrosion in the metal. The corrosion of metal, for instance of an aluminum surface, produces particles which contribute to a severe contamination problem for the main chamber
32
where a wafer is positioned.
It is therefore an object of the present invention to provide a plasma etch chamber that does not have the drawbacks or shortcomings of a conventional plasma etch chamber.
It is another object of the present invention to provide a plasma etch chamber that is equipped with a middle chamber that has significantly reduced particle contamination problem.
It is a further object of the present invention to provide a plasma etch chamber that is equipped with a middle chamber and a main chamber which has significantly reduced contamination problem by evacuating residual etchant gas from the middle chamber.
It is another further object of the present invention to provide a plasma etch chamber that is equipped with a middle chamber for feeding an etchant gas plasma into a main chamber that has significantly reduced particle contamination problem.
It is still another object of the present invention to provide a plasma etch chamber that has a middle chamber and a main chamber equipped with a bypass exhaust conduit connecting the middle chamber to the main chamber.
It is yet another object of the present invention to provide a plasma etch chamber that has a middle chamber and a main chamber in fluid communication through an apertured opening and a bypass exhaust conduit.
It is still another further object of the present invention to provide a method for preventing corrosion in an etch chamber by residual etchant gas wherein the etch chamber is equipped with a middle chamber and a main chamber.
It is yet another further object of the present invention to provide a method for preventing particle contamination in an etch chamber by providing a bypass exhaust conduit connecting between a middle chamber and a main chamber such that residual etchant gas can be evacuated from the middle chamber.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus and a method for
Hassanzadeh P.
Mills Gregory
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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